1. Field of the Invention
The present invention relates generally to communications technology for interconnecting data processing terminals including personal computers and mobile data terminals, and more specifically to a technique for establishing a session between such terminals in a client-server relationship when a predetermined mutual proximity is satisfied.
2. Description of the Related Art
While data communications technology has evolved from long-haul peer-to-peer connections and progressed through LAN and WAN to the recent internet connections, study has recently been focused on a technology for establishing secure connections between data terminals mutually located at close range. Because of the increasing importance of security, this technology will open up ways for developing a wide range of future applications. Typical examples of the prior art technology for establishing close-range connections involve the use of a wireless medium such as an infrared light beam of high directivity and weak electromagnetic radiation, as disclosed in Japanese Patent Publication 1999-150547. However, if it is desired to ensure high transmission speed, each communications terminal must be equipped with a high-precision, low-power wireless transceiver. Since the high-precision RF (radio frequency) transceivers represent a significant amount of expenditure, this prior art is disadvantageous for a local area network if the user desires to additionally establish an individual wireless link between a mobile terminal and a nearby LAN terminal. Furthermore, due to the characteristics of the high-precision transceiver, difficulty will be experienced when installing a radio transceiver on each LAN terminal.
Japanese Patent Publication 2002-125268 discloses a technique in which infrared communication is used to identify each communication terminal and a session (link) is established through a Bluetooth wireless network between terminals by using their identifiers. Since the infrared communication is only required to acquire a terminal identifier from a nearby terminal, a simple low-cost infrared transmitter may be sufficient. However, once a mobile terminal has acquired a terminal identifier from a nearby network terminal, a session can be established between them through the Bluetooth network even though they are separated significantly from each other in so far as their distance is in the communication range (10 to 100 meters). This is disadvantageous for applications where secure communication is important.